Solid oxide fuel cells (SOFCs) operate at high temperatures which are generally in the range of about 750° C. to about 1000° C. These high temperatures are challenging to the materials employed, and are of particular concern with regard to the stability of the anode structures. For fuel oxidation, the so far preferred anode material comprises metallic nickel. Nickel is also preferred for reformed hydrocarbon fuel since it is a good catalyst for hydrocarbon reformation.
Manufacture processes suggested in the prior art include the provision of a support, the formation of an anode layer thereon, followed by the application of an electrolyte layer. The so formed half cell is dried and afterwards sintered, often in a reducing atmosphere. Finally, a cathode layer is formed thereon so as to obtain a complete cell.
However, during the sintering of the half cell, undesired reactions between the metal support and anode materials may occur, resulting in a negative impact on the overall cell performance. Moreover, in the prevalent anode supported design, oxidation of the anode is known to be detrimental for the cell performance. The above mentioned method constitutes some limitations on the anode material to be used.
US 2002/0048699 discloses a solid oxide fuel cell comprising a ferritic stainless steel substrate including a porous region and a non-porous region bounding the porous region. A ferritic stainless steel bipolar plate is located under one surface of the porous region of the substrate and is sealingly attached to the non-porous region of the substrate above the porous region thereof. A first electrode layer is located over the other surface of the porous region of the substrate, an electrolyte layer is located over the first electrode layer and a second electrode layer is located over the electrolyte layer. While such a solid oxide fuel cell is relatively cheap and avoids the use of brittle seals, the SOFC it is not sufficiently robust. The teaching of US 2002/0048699 furthermore does not overcome the above mentioned problems related to the manufacturing process of the SOFC.
WO-A2-2005/122300 relates to a solid oxide fuel cell comprising a metallic support ending in a substantially pure electron conducting oxide, an active anode layer consisting of doped ceria, ScYSZ, Ni—Fe alloy, an electrolyte layer consisting of co-doped zirconia based on an oxygen ionic conductor, an active cathode layer, and a layer of a mixture of LSM and a ferrite as a transition layer to a cathode current collector of a single phase LSM.
WO-A1-2004/030133 discloses a fuel cell supported on the electrode side, comprising a cathode support, a cathode layer, an electrolyte layer and an anode layer in this order. The cathode is preferably applied employing a printing technique.
In view of the prior art, there is still a need for more freedom in choice of suitable materials and design of an SOFC, especially the anode part thereof.